330 New Theory concerning the [June, 
Froid,” published in the Transactions of the Association 
Frangaise for 1881. The following is his method of esta- 
blishing the periodical recurrence of the changes : — He first 
plots off the daily mean temperature of twenty years’ ob- 
servation, and draws a curve to represent the annual march 
of the temperature, increasing from January ioth until July 
29th, and then decreasing. It thus is rendered manifest 
that the mean temperature rises and falls as compared with 
this smooth curve of hot and cold resulting from the advance 
and retreat of the sun, and that these rises and falls of tem- 
perature, broadly speaking, have a tendency to recur at the 
same times of the year. 
Having the dates of some hundred eruptions of Etna and 
Vesuvius by me, I bethought me to compare them with the 
warm and cold periods of the year as determined by Prof. 
Ragona. Since, according to Messrs. Mallet and Perrey, we 
have more earthquake shocks during the winter than in 
summer, I fancied, as I previously intimated, to see the 
dates tally with the cold periods, whereas what was my sur- 
prise to see them all huddled together at the warm ones ? 
I therefore transposed M. Ragona’s two tables, so as to show 
the warm periods of the year only at Modena, and then 
compared them with one another and with my chronicle of 
eruptions, and I discovered a certainly general concordance. 
The following were my conclusions : — A period of warmth 
attended with increased activity on the part of Vesuvius or 
Etna may be looked for about January 8th, of a few days’ 
duration ; and another following the 20th of the month, ter- 
minating about February 8th. The next may be expected 
about February 12th, lasting until March 16th ; followed by 
another commencing on March 21st, and continuing until 
April 6th. The next may be expected about April 24th, and 
the next at the commencement of May, the last indicating 
about two weeks of volcanic activity, followed by a pause, 
and then renewed activity about the 24th, continuing until 
the end of the month, or protracted into the first two weeks 
of June. Another period of warmth and volcanic activity 
may be expected to set in about June 20th, lasting some four 
or eight days. The week following July nth may be ex- 
pected to be one of warmth and volcanic activity, and like- 
wise the two weeks following the 26th. Another period 
may be looked for about August nth, lasting for about two 
weeks, and another the first week in September. The week 
following September 20th and the week following October 
ioth are marked by eruptions, and correspond to, but hardly 
coincide with, two periods of warmth in M. Ragona’s first 
